Question

A bulb connected in series with a solenoid is lit by a.c. source, Fig. If the soft in core is introduced in the solenoid, will is bulb glow brighter ?

Answer 1

We know that the inductive reactance offered by the solenoid is `X_(L) = omega L = 2 pi v L`. On introducing soft iron core in the solenoid, its inductance L increases. Therefore, `X_(L)` increases As `I_(upsilon) = E_(upsilon) // X_(L)`, therefore, `I_(upsilon)` decreases. As glowing power of bulb `= I_(upsilon)^(2) R`, therefore, the bulb glows dimmer, and not brighter :